Draft gear



Jan. 18, 1927.

W. H. COTTON DRAFT GEAR Jan. 18, 1927. W. H. COTTON DRAFT GEAR FiledJan. 28, 1924 2 Sheets-Sheet 2 r time of their application.

Patented Jim. 18,1927.

WALTER H. COTTON, F CHICAGO, ILLINOIS.

DRAFT GEAR.

Application led January 52.8,` 1924. Serial N'o. 689,042.

T he invention relates to draft gear for railway cars, and isparticularly adapted Ifor use in passenver service. The gear is of theso-called hydraulic type, in which a liquid, preferably an oil,constitutes in part the shock-absorbing agent.

While it has been possible to design draft gears of the metallicfriction type of very high capacity for absorbing shocks, the parts ofsuch gears are not always in the proper relative position to performWork. As a consequence, in passenger service, great annoyance anddiscomfort of the occupants of a train is occasioned by the suddenapplication of high power, as in an effort to set a heavy train inmotion, and by a sudden checking of the movement of the train. as by anemergency application of the brakes or in coupling operations.

ln many types of gears the recoil is sutliciently abrupt to causeannoyance and discomfort, and this trouble is accentuated when themovement of the train is suddenly arrested while the gear is undercompression, as the arresting force meets with no resistance in the gearuntil the recoil has taken place.

The objects of the present invention are to eifectively overcome these'disadvantages in existing practice by securing a smoothness of action,the prevention of abrupt and sudden movement of parts of the gear, andthe arresting of sudden shocks in whatever position the partsof the gearmay be at the A further object is to provide for a cushioning of thegear as it approaches the limits of its compression, and a still furtherobject is to reduce to a minimum the leakage of liquid in a hydraulicgear.

'These various objects are secured by a construction such as ishereinafter described, and as illustrated in the accompanying drawings.in which- Fig. 1 is a vertical central longitudinal section of the gear,details of associated parts of the car being shown partly in elerationand partly in section;

Fig. v2 is a plan view of the. gear with details of associated parts;

Fig. 3 is a view similar to Fig. 1, the parts being shown in differentpositions;

Fig. 4 is a sectional view-on the line 4-4 of Fig. 3; and

Fig. 5 is a sectional view on the line 5-5 of Fig. 1.

The gear comprises a cylinder 10, which is adapted to be secureddirectly to a pair of draft sills l1, 11, the cylinder being pro- 'videdwith a pair of lateral attaching plates '12, 12, which may fit againstand be bolted to flanges of the sills. vThe cylinder is located between,and constantly bears against, a pair of draft lugs 13, 13, and a pair ofbufling lugs 14, 14, which are fixed to the draft sills.

Within the cylinder there reciprocates a piston 15, the stem 16 of whichprojects forwardly and is attached, as by meansl of a key 17, to anelement of a coupler 18. The coupler may be'of any preferred form ofconstructiomvand the particular manner of attaching the piston stem toit is not the essence of the invention.

The' cylinder 1() is filled with a liquid, indicated at 19, which iscaused to shift from one end of the cylinder to the other by suitableby-passes, by the movement of the piston, under the influence of draftor buiiing stresses transmitted to it through the coupler. The liquidused vis preferably an oil which is but slightly changed in` itsconsistency by variations in temperature.

Springs are employed for resisting the movement of the gear in eitherdirection from normal or central position`l and for re storing the partstosuch position when the forces to be iesisted have ceased to act. Asshown, and, so far as now advised, preferably these springs 20,21, areinclosed within the cylinder, are helical-in form, and react between theopposite faces of the piston and the ends of the cylinder. The forwardspring, 20, encircles the stem 16 of the piston. and preferably thelatter is encased in a loose sleeve 23 for preventing abrasion of thestem 16. The rear spring, 21, here shown as a pair of nested springs` isheldv ward extensions 29, 30, the tops of which are closed by caps 31,32. These caps constitute seats for springs 33, 34, which react u on andresist the opening of a pair of-va ves 35, 36, controlling a pair ofports 37, 38, of com aratively large size, in the cylinder wal andlocated, respectively, adjacent its ends.

A. pair of smaller ports 39, 40, are locate respectively, on oppositesides of the norma or central position of the piston 15, and open to thedisplacement chamber 27 These ports may be positioned in any convenientlocation, and are shown as .opening through the walls of the hollowstems of the valves 35, 36. The ports 39, 40, provide the initial pathof transfer of the liquid from end to end of the cylinder. Under theinfluence of severe stresses one of the valves 35, 36, will bedisplaced.

Ducts 41, 42, lead from the chamber 27 around the vcylinder walls to apassage 43, cored in' the lower wall of the cylinder and leading to apair of ports 44, 45, which open to the cylinder chamber adjacent itsopposite ends, these ports being controlled by a pair of inwardlyopening valves 46, 46, which are held to their seats by light springs,as 47 the free inflow of liquid back of the advancin piston being thusprovided for. The va ves 46, 46, are carried by casings 48, 49, whichmay be screwed into suitable openings in the cylinder wall.

The piston stem 16 plays through a stu'- ing box 22, which prevents theleakage of liquid from the cylinder. lit has been found in practice thatin devices of this general character it is impossible to entirelyprevent leakage by means of a stuiiing box, and in this instance such adevice is supplemented by a receiving chamber 50 at the inner end of thebox, from which chamber leads a duct 51 to the conserving chamber 27. Ateach side of the chamber 50 the eX- tended neck of the cylinder, whichconstitutes a part of the stuiling box 22, is provided with an annularrib 52, 53, which makes a close but easy fit upon the stem 16.

While the forward movement of the piston 15 will cause the escape of asmall portion of the liquid content of the cylinder intothe chamber 50,such liquid is free to pass into the chamber 27, within which there isat no time any appreciable development of pressure, and, consequently,the stufling box 22 is not required to resist any serious liuidpressure.

While, in the form. of construction shown, the duct or pipe 51 provides'adequate escape for the liquid from the chamber 50, the relief duct fromthis chamber may be formed in or through any of the parts of the device,whether movable or stationary, providing it will deliver directly oreventually to either side of the piston.

It is unnecessary to provide the piston 15 with packmg or sealing rings.rlhe piston may make merel a close t with the cylinder, and inasmuc asthe action of the device 1s dependent u on the transfer of liquid fromend to en of the cylinder, it is quite permissible that this transfer mabe provided for in part by leakage past t e piston.

Inasmuch as the piston rod 16 is necessarily of considerable diameter,in order to provide adequate strength, it has the effect of reducing thearea of the front face of the iston. The piston being thus of thediferential type, the displacement of liquid on its forward or outstrokeis less than on its backward or instroke. On the outstroke, therefore,no more liquid is drawn from the displacement chamber 27 through theport 45 than is delivered to it through the ports 37 or 39, while on theinstroke there is less liquid delivered through the port 44 than is,forced into the chamber 27 through the ports 38 or 40. For this reasonit is important that in supplying the device with oil it should notentirely lill the displacement chamber, and in practice the normal levelof the liquid should be approximately as shown in Fig. 3. A llingopening is provided in the top wall of the casing 28, and is shown asnormally closed by means of a plug 54. A drain opening is provided inthe bottom wall of the cylinder, communieating with the passage 43, andis normally closed by means of a screw plug 55.

Inasmuch as no dependence is placed upon l the compression of air withinthe displacement chamber, the two upward extensions 29, 30, may, ifdesired, be merged together. ln any event, however, it is desirable thatthe filling opening be so located as to prevent filling beyond' asuitable level.

The normal or constant pull of the engine is resisted by the spring 20,which should exceed in capacity the normal tractive eflort of thelocomotive.

In Fig. 3 the piston is shown in the position it occupies when the trainis being drawn forward at approximately uniform speed.A Should anysudden shock occur tending either to accelerate or check the trainmovement, one'of the valves 35, 36, will be opened to an extentcorresponding to the intensity of the shock, which will be absorbed bythe combined resistance of thc piston spring which is compressed, thespring of the unseated valve, and the movement 'of the fluid through theopened port and to the opposite end of the cylinder. Any severe shocks,occurring at whatever status of the train, are taken care of in likemanner.

When the car is standing thepiston 15 will assume the central position,as shown in Fig. 1. As the car is drawn forward the sov should there bea quick succession of shocks,

due to variations in pull or buff or the sudden reversal of the engine,before the springs could restore the piston to central'positon, theywill be resisted and absorbed by the liquid as effectively as ifcomplete restoration vhad occurret.

The flanges 25, 26, are of such length and diameter that they enter andmake a aufliciently close t with the reduced diameter of the ends of thecylinder to serve as limitin stops by trapping the liquid within the cyinder end, thus defining the range of movement 'of the piston, or atleast preventing violent contact of the piston with a positive stop.

While an efficient and, so far as I am advised, a preferred form ofconstruction, is disclosed, various changes in the form and yarrangement of the parts may be made within the scope of the invention.For example, while the ports 39, 40, are shown as communicating with thedisplacement chamber, this is for simplicity in manufacture,- it beingnecessary only that each shall communicate with the opposite end of thecylinder.

I claim as my invention- 1. In a hydraulic device for absorbing shocksof variable intensity, in combination,

a cylinder, a piston reciprocable in the cyl-I inder, a by-pass of smallcapacity connecting the end portions of the cylinder at opposite sidesof the normal position of the. piston, a similarly arranged by-pass oflarger capacity, outwardly opening pressure-seated valves for the portsof the larger by-pass, and means for returning the parts tonormalposition after compression.

2. In a shock absorbing device, a cylinder, a pistonv for said cylinder,a chamber having ports in communication with said cylinde!` at oppositesides of the normal position of said piston, normally closed valves forsaid ports, and means for restoring the parts to normal position aftercompression of said device.

3. In a hydraulic device for absorbing shocks of variable intensity, incombination, a cylinder, a differential piston reciprocable therein, adisplacement chamber, ports connecting thev end portions of the cylinderwith suoli chamber, normally closed valves for such ports, the chamberbeing provided with an extension above the normal level of the containedliquid, and means for returning the parts to normal position aftercompression.

4. In a hydraulic draft gear, in combination, a cylinder, a reciprocablepiston in the cylinder, tain a liquid for retarding the movement of thepiston, a by-pass being provided for the transferof the liquid from sideto side of the piston, normally closed valves for said by-pass andspring means resisting the advance of the piston and being of sufficientcapacity to sustain the normal pulling stresses.

5. In a hydraulic draft gear, in combination, a cylinder, a reciprocablepiston in the cylinder, such cylinder being adapted to contain a liquidfor retarding the movement of the'piston, aby-pass being provided forthe transfer of the liquid from side to side of the piston, spring meansresisting the advance of the piston and being of. sufficient capacity tosustain the normal pulling stresses, a supplemental by-pass, andspringclosed valves for the ports thereof.

6. A hydraulic draft gear, comprising a cylinder having its bore reducedadjacent its ends, and a piston reciprocable in the cylinder land havingan imperforate annular flange projecting from each face of approximatelythe diameter of the reduced end portions of the cylinder and adapted totelescope the same, and means for restoring the piston to centralposition after displacement therefrom.

7. A hydraulic draft gear, comprising a cylinder having its bore reducedadjacent its ends, the reduced portions being unported and animperforate piston reciprocable in the cylinder and having a projectionon each face of approximately the diameter of the reduced end portionsof the cylinder and adapted to telescope the same, and means forrestoring the piston to central position after displacement therefrom.

8. In a hydraulic draft gear, in combination, a cylinder, a displacementchamber above the cylinder, a plurality of ports differentiated in sizeconnecting each end portion of the cylinder with the chamber, the largerports being normally closed by springseated outwardly opening valves,the cylinder being provided with ports near each end normally closed byinwardly opening valves, a passage leading from the displacement chamberto each of the last-named ports, and a piston reciprocable in thecylinder.

9. In a hydraulic draft gear, in combination, a cylinder, a displacementchamber above the cylinder, a plurality of ports differentiated in sizeconnecting each end porsuch cylinder being adapted to conliu tion kofthe cylinder with the chamber, the larger ports being normally closed bysprlngseated outwardly opening valves, the cylinder being provided withports near` each end normally closed by inwardly opening valves, apassage leading from the displacement chamber to each of the last-namedports, a piston reciprocable in the cylinder, and springs acting on thepiston to normally osition it approximately central in the cylinder andbeing of suflicient capacity to resist the normal stresses of draft.

10. In a draft gear, in combination, a cylinder adapted for fixedattachment to a car, a piston reciprocable in the cylinder and having astem for attachment to a coupler, springs for urging the piston tocentral position, a displacement chamber associated with the cylinder,comparatively restricted ports connecting the cylinder and displacementchamber at opposite sides of the normal piston position, a pair oflarger ports leading from the end portions of the cylinder to thechamber, outwardly opening spring-closed valves for the largerports, apair of return ports communicating with the end portions of the cylinderand with the chamber, and normally closed inwardly opening valves forthe last-named ports.

11. In a draft gear, in combination, a cylinder, adapted for fixedattachment to a car, a piston reciprocable in the cylinder and having astem for attachment to a coupler, centering springs reacting between thepiston and the ends of the cylinder, a displace' ment chamber associatedwith the cylinder, ports connecting the cylinder and displacementchamber at opposite sides of the normal piston position, a pair oflarger ports leading from the end portions of the cylinder to lthechamber, outwardly opening spring-closed valves for the larger ports, apair of return ports communicating with the end portions of the cylinderand with the chamber, normally closed inwardly-opening valves for thelast-named ports, a stuffing box through which the stem of the pistonprojects and having a chamber intermediate of its ends, and a ductconnectin such chamber with the displacement cham er.

12. In a draft gear, in combination, a cylinder adapted for fixedattachment to a car, a piston reciprocating in the cylinder, a bypassconnecting the end portions of the cylinder, a Stufiing box having achamber intermediate of its ends and being normally out of communicationwith the cylinder chama pistonv reciprocating within the cylinder andhaving a stem for attachment to a draw-`V bar, a spring for resistingthe forward movement of the piston and having sufficient capacity toresist the normal draft for moving a car to which the gear is attached,a by-pass connecting-opposite ends of the cylinder, and a spring-seatedcheck valve in the forward end of the by-pass.

4 14. In a hydraulic draft gear, a cylinder, a piston for said cylinder,a chamber having comparatively large ports in communication with saidvcylinder at the end portions thereof, valves for said ports, yieldingmeans for normally holding said valves in closed position', and meansfor restoring the piston to normal position after compression.

15. In a hydraulic draft gear, a cylinder for containing a liquid, apiston for said cylinder, a displacement chamber having inlet and outletports for said cylinder, said inlet ports being located below the normallevel of the liquid in said cylinder, springpressed valves for saidports, and means for restoring the parts to normal position aftercompression.

16. In combination, a cylinder having a by-pass connectin its ends and apiston reciprocating therein and adapted to move vsis liquid through theby-pass, a stuffing box pressing means, a stuffing box in the wall ofthe casing through which the shaft projects,

such stuffing box having a chamber through whichthe shaft directlyextends and which is normally out of communication with thc chamber ofthe casing and isprovided with an outlet delivering to a chamber'under'less pressure than that developed in the first named chamber and incommunication there-Y with.

WALTER H. coTToN.

CERTIFICATE OE CORRECTION.

Patent No. 1,614,657, granted january Is, 1927.

to WALTER H. COTTON.

lt is hereby certified that error appears in the printed specification-of the above mentioned patent requiring correction as follows: Page 3,line 108, claim 7, strike out the words "an imperforate" and insert thearticle "a", and line 109, strike out the article "a" and insert insteadthe words "an imperforate"; and that the said Letters Patent should beread with these corrections therein that the same may conform to therecord of the case in the Patent Office. Signed and scaled this 22nd dayof February, A. D. 1927.

M. J. Moore,V Seal. Acting Commissioner of Patents.

